Yoma 46B

טומאה, דתחילתו בר מידחא טומאה הוא ⁠— סופו נמי דחי. שבת, דתחילתו לאו בר מידחא שבת הוא ⁠— סופו נמי לא דחי.

Therefore, with regard to overriding the prohibition to bring an offering in a state of ritual impurity, since the beginning of the sacrifice of the daily offering is fit to override the prohibition of offering it in a state of ritual impurity, so too, its end also overrides the prohibition. However, in the case of Shabbat, the beginning of a daily offering of the weekday is not fit to override Shabbat, since by definition it must be brought on its appropriate day. Therefore, its end also does not override Shabbat in the event that limbs remain from Friday’s daily offering.

לרב חסדא לא קשיא: סופו כתחילתו (תחילתו) לית ליה. שבת דהותרה היא בציבור ⁠— סופו נמי דחי.

And it is also not difficult to the opinion of Rav Ḥisda, because he does not hold that its end is like its beginning. Rather, he has the following reasoning: The prohibitions of Shabbat are not merely overridden in the case of a communal offering, but they are actually permitted, such that there is no need to try to avoid performing the necessary labors when sacrificing it. Therefore, its end also overrides Shabbat.

טומאה, דדחויה היא בציבור, תחלתו דעיקר כפרה ⁠— דחי, סופו דלאו עיקר כפרה ⁠— לא דחי.

However, in the case of the prohibition to bring an offering in a state of ritual impurity, which is merely overridden in the case of a communal offering, it is preferable to avoid doing so. Therefore, the beginning of its sacrifice, i.e., its slaughter and the sprinkling of its blood, and its burning, which is the essential stage that provides atonement, overrides the prohibition and should be done even in a state of ritual impurity. However, its end, i.e., the burning of the sacrificial parts, which is not the essential stage that provides atonement, does not override the prohibitions.